1. Field
The present invention relates generally to wireless communications, and more specifically to reducing transmit power and improving data rates in wireless communication systems.
2. Background
Minimizing transmit power and improving the data rate is a concern for all mobile devices. Specifically, dual-antenna mobiles must find the best way to utilize two transmit antennas to transmit information to the base station. This transmission method is known as Mobile Transmit Diversity (MTD) or Uplink Transmit Diversity (ULTD). The mobile device either selects the best antenna at any given time, or transmits from both antennas using the best beam forming phase. Currently, base stations do not provide feedback to mobile devices for optimizing antenna or phase selection. Without feedback from the base station on which antenna to transmit from or which phase to use if using two antennas, the mobile is operating in Open Loop MTD. In Open Loop MTD operation, the mobile device must autonomously determine the best antenna configuration and phase value for transmitting information.
Prior algorithms for optimizing antenna configuration and transmission phase have been found to be inordinately slow and/or inaccurate as well as the cause of phase tracking problems at base stations. There is therefore a need in the art for an Open Loop MTD transmission algorithm capable of operating at higher mobile data rates and maintaining base station phase tracking.